One step furter to allow saving of orders w/o explicit recurringperiod

uncloud_pay/migrations/0031_auto_20201006_1655.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.1 on 2020-10-06 16:55
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_pay', '0030_auto_20201006_1640'),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name='producttorecurringperiod',
+            constraint=models.UniqueConstraint(fields=('product', 'recurring_period'), name='recurring_period_once_per_product'),
+        ),
+    ]